1. Field of the Invention
The present invention relates to a series of high performance polymeric materials derived from norbornene derivatives, particularly, the present invention relates to novel functional norbornenes as initiators for radical polymerization, their polymer and a process for producing the same.
2. Description of Related Art
Up to now, polycarbonate (PC) has been used as macromolecular material for optical purpose. The most important considerations, which may influence the use of the optical material, include birefringence and water adsorption. Accompanying with the development of high-density compact disk, it becomes more and more difficult for those prior art polymers to meet the requirements. Hence, it is desirable to develop a polymeric material having lower birefringence and water absorption.
For this reason, a commercial material ZEONEX has been developed in Japan (Nippon Zeon). It is the polynorbornene which has lower birefringence, lower water adsorption and better optical characteristics. Such material can be prepared by ring-opening metathesis polymerization of a norbornene monomer in the presence of a metathesis catalyst and hydrogenated to become a saturated polynorbornene.
Along with the development of high-density compact disk, a method for producing a new polymeric material with lower birefringence and high transmittance for low wavelength range (blue light) is developed. The polynorbornene is such a noncrystal optical material that its transmittance with respect to the light having a wavelength of about 400 nm may approach to 90%. The reason is that there is no aromatic ring contained in the main chain. In addition, there is also no hydrophilic functional group contained in the main chain of this polymer, so the ratio of water adsorption may approach to a value below 0.01%. Under the same condition, the polynorbornene has water absorption ratio far lower than that of the polycarbonate (PC). In the aspect of heat resistance, the glass transition temperatures of the polynorbornene and polycarbonate (PC) fall within the same temperature range (about 123° C.). Hence, there is a need for the development of such a material in the industry at the present time and in the future.
In recent years, attention has been paid to hydrogenated products of polymers produced by ring-opening metathesis polymerization of norbornene-type monomers such as tetracyclododecene, dicyclopentadiene (DCP), and tricyclopentadiene, etc. These hydrogenated products can serve as an optical material for use in an optical disk, optical lens, or transparent film, etc. (please refer to JPO60-26024, JPO1-24826, JPO63-264626, EP303, 246, JPO-63-317520 and JPO-1-132656). The reason therefore is that such hydrogenated products have excellent transparency and heat resistance and hardly susceptible to moisture gain and that they have comparatively small briefringence and excellent moldability.
Olefin metathesis polymerization is a popular method in polymer synthesis. In recent years, the ring-opening metathesis polymerization of cycloolefin and the metathesis polymerization of non-cyclodiolefin are become very important in polymer synthesis. Accompanying with the developments of new catalysts, the synthesis method of polymeric materials which contain various functional groups is developed correspondingly.
Organometallic catalysts have been used in metathesis polymerization for a long time. However, those organometallic catalysts are not suitable in metathesis polymerization of the monomer which contains various functional groups and is also sensitive to moisture and oxygen gas. For example, tungsten (W), titanium (Ti), molybdenum (Mo) and ruthenium (Ru) catalysts are the most popular catalysts are used in the ring-opening metathesis polymerization of cycloolefin, wherein, ruthenium (Ru) catalyst is the most tolerant catalyst with respect to water and oxygen gas in the metathesis polymerization. The metathesis polymerization can even be carried out in an aqueous solution in the presence of ruthenium (Ru) catalyst. For example, the catalyst of {Cl2Ru(CHPh)[P(C6H11)3]2} developed by Grubbs et al. in 1996 is good for ring-opening metathesis polymerization of cycloolefin. More particularly, the polymerization of the monomers with functional groups can be carried out in the presence of such a catalyst because it is stable in the air. In addition, such metathesis polymerization has a property of high polymerizing rate and large molecular weight of resulting polymer. Generally speaking, such reaction has accompanied with living polymerization.
The ring-opening metathesis polymerization of a norbornene-type monomer is carried out, in general, in the presence of (1) a catalyst system consisting of an organometallic compound such as an organoaluminum compound and a tungsten and/or molybdenum-based metathesis catalyst (please refer to JPO46-14910) or (2) a catalyst system containing an organometallic compound such as an organoaluminium compound and a transition-metal compound such as titanium tetrahalide (please refer to JPO41-20111 and JPO50-12199).
However, in the case of the ring-opening polymerization using the first kind of catalyst system as described above, the resultant polymer has a broad distribution of molecular weight and thus has high birefringence, in spite of an advantage that the polymer can be obtained at such high yields that the residual monomer is hardly present in the reaction system when the reaction has completed.
In the case of the ring-opening polymerization using the second kind of catalyst system as described above, the molecular weight distribution of a resulting polymer can be easily controlled. However, as the concentration of a monomer in the reaction system decreases, the rate of polymerization also decreases greatly. Hence, polymers by the ring-opening metathesis polymerization (ROMP) of the present catalyst system cannot be obtained in high yields. Moreover, a large amount of unreacted monomers remains in the reaction system when the polymerization has completed. It is very difficult to remove this unreacted monomer during the purification of the polymer.
Hence, the extensive research on ring-opening metathesis polymerization (ROMP) of cycloolefin derivatives to improve the reactivity of catalyst. The research mainly also focused on the development of side-chain-type liquid crystal, a triblock copolymer synthesized by two-step method, a polymer with various functional groups and a polymer having cross-linkable functional groups remained in the side chain thereof, etc. The introduction of the functional groups improves the optical characteristics and biochemical activity of the polymer. In addition, the cross-linkable functional groups such as methacryloyl in the side-chain can be introduced and applied as UV curing agent, coating material and photoresist.
The polynorbornene and its derivatives are the first commercial products by ring-opening metathesis polymerization (ROMP). They are one of the important engineering materials. Those materials are used with shape-memory polymers, shining apparatus, machine, electrical elements, tube, food packages and the like because of their good transmittance, large usable temperature range, good mechanical property and excellent moldability. In addition, the derivatives of polynorbornene such as acidic and aromatic polymers can serve as a photoresist and can be used in semiconductor manufacturing process.
Although the polynorbornene and its derivatives have good transmittance, wider usable temperature range, good mechanical property and excellent moldability, the technology of synthesizing new norbornene-type monomer and its polymers are not well developed and the problems associated with the preparation of the polymer are not easy to overcome. Hence, the development of new norbornene-type monomers and their derivatives has great potential in various applications.
The present invention provides novel functional norbornenes as initiators for radical polymerization, its polymer and a process for producing the same. More particularly, the polymerization of novel functional norbornenes in the present invention can be selectively carried out by ring-opening metathesis polymerization (ROMP) or radical graft copolymerization to obtain various polynorbornene derivatives (Macromonomer, macroinitiator, homopolymer, random copolymer and block copolymer) or grafted copolymer materials (Branched polymeric materials). The polynorbornene derivatives and grafted copolymer materials not only exhibit excellent functional properties but also enhanced physical and chemical properties after modification.